Instructions to Build a Gold Probe
Directions for building of your own handheld electronic hole probe

Parts needed:

  • AMPROBE metal detector (Grainger's PN 5U777) - ($20.00) by GB products WIRE and PIPE detector GPD- 902 1 believe or HOME DEPOT A.W. Sperry PF-2a ($12.97)

  • 12" piece of PVC 1/2" diameter water line - .50

  • Two end caps to match- .34

  • Dab of PVC glue (optional)

  • Squirt of solder -. 10

  • 4 pieces of about #20 wire-each 15" long- .35

  • 2 pieces 1/8" bolts 1-3/4" long- .30

  • Nuts / star washer to match - .05

Tools needed:

  • Soldering iron

  • Hand drill with bits

  • Wire cutters/strippers

  • Screwdrivers regular and phillips

  • Bench grinder (optional)

Work Time:

  • 1.5 hours

PLEASE READ ALL INSTRUCTIONS BEFORE STARTING THERE ARE HINTS WHICH MAKE THINGS GO EASIER.

Directions:

  1. Purchase the AMPROBE from Graingers (on the web)..or a local store.

  2. Familiarize yourself with its operations - you may wish to use it as - is.

  3. If you wish to modify it.., here's how.

  4. Remove battery.

  5. Unscrew case cover (one screw is hidden under the logo sticker) (No screw in the LOWES probe)

  6. You will find a small primed circuit board wired to a ferrite antenna.

  7. Remove screw holding circuit board in place.

  8. Gently lift out circuit board and antenna.

  9. Antenna will have a small separate phenolic board lightly glued to it, remove the board with a gentle prying with a screwdriver (This phenolic board is the VOLTAGE detector)

  10. The phenolic board will have a single insulated wire soldered to it. Remove the single wire (cut) and discard. Now discard the tiny phenolic board, it is not needed. If you are using the LOWES probe, there is no phenolic board...just clip off the black wire on the "Voltage" end.

  11. You will see that the ferrite antenna is attached to the large circuit board with 4 annealed copper wires... we must lengthen the wires.

  12. Notice where the 4 wires are soldered to the circuit board... there is a number on the board at each of the 4 points... using masking tape, label the 4 wires with the proper number.

  13. Now you may unsolder the 4 copper wires from the board.

  14. Using your solder iron, "lengthen" each of the 4 wires, using a 15" piece of #22 (approx.) of insulated wire, Re-label your wires at the new ends. 15. Now set the antenna assembly aside to cool.

  15. Now get your 12" piece of PVC.

  16. You will need to drill 2 holes in the PVC - for your bolts.

  17. Place the PVC caps on the pipe. DO NOT GLUE YET.

  18. Hold the pipe up against the AMPROBE body as shown in the picture to determine about where to drill your bolt mounting holes thru the pipe I drilled my holes in the pipe about 2" and 4" from the end of Pipe cap.

  19. Mark and drill your holes... to match your bolt diameters... thru the centerline of the pipe in on side and out the other (2 walls).
  20. Test your bolts to fit.

  21. You now will need to a bigger hole in the pipe... in between the two smaller holes. The bigger hole is needed to pass the 15" wires thru, choose the proper drill bit size. BUT THIS TIME DO NOT DRILL THRU BOTH PIPE WALLS, JUST ONE WALL.

  22. Now we will drill accommodating holes in the AMPROBE shell to match the bolt holes and wire hole in our pipe. Reassemble the two halves of the AMPROBE shell and screw together.

  23. You now must mark the shell with a scriber/pencil to show where to drill... and drill the holes. I FIND YOU MUST DRILL THE SHELL "bolt" HOLES (2) off/center of the seam... so that the 2 bolt holes will be solely in one half shell or the other... not on the seam. IT IS BEST TO DRILL the 2 bolt holes in the HALF SHELL with the mounting post for the circuit card.

  24. Now that you have tested the shell and pipe for mating/bolting OK.

  25. Remove the PVC endcaps... take the antenna assembly, and stuff the 15" wires thru the UNDRILLED end until they appear at the drilled "wire hole"... pull them thru the wire hole gently while sliding the ferrite antenna into the pipe.

  26. Smear the ferrite antenna with RTV or some caulk as it enters the pipe. position it "flush" with the pipe end recoat with RTV. to hold in place and provide "shock absorption"

  27. Let the RTV dry

  28. Put the endcaps back on the pipe.

  29. Unscrew the AMPROBE shell.

  30. Align the bolt holes in the 1/2 shell with the bolt holes in the pipe... and attach pipe to the 1/2 shell.

  31. Fish the 15" wires into the 1/2 shell thru the wire hole.

  32. Cut/strip the 15" wires to proper length, for attaching to circuit card.

  33. Solder wires to the 4 points on the circuit card, using your masking tape ID labels, for reference.

  34. Screw circuit card into halfshell.

  35. Attach other half shell and screw closed.

  36. Re-affix logo label.

  37. Cement end caps if you wish... I did not find it necessary.

  38. Replace battery. and test.

  39. Have fun!
Note...
For those who have a bench grinder. I ground the pipe "fiat' at the mating area where it meets the AMPROBE shell this created a "fiat" which was more accommodating as a mating/bolting surface. By doing this it also ground away the bolt holes and wire hole on the mating wall of the pipe facing the shell leaving a "open slot"
The bolts and wires passed thru the slot easily and the unit still was "rigid" I put a little RTV around the slot for waterproofing. Also, you can make a power saver option by installing a mini-Push Button switch in series with the red battery wire Switches can be bought at Radio Shack. This will allow you to set he sensitivity of the thumbwheel only once and then use the P/B to activate the power saves wear and tear on the thumbwheel switch.
Those that want a "light" can buy a 9V mini lamp and install in the case wiring in parallel with the circuit card. Or use a White L.E.D. with appropriate series resistor. Experiment, its fun!!!!
Mine works super 1/2 to 1" for coins in the dirt hole deeper for bigger items!!
by DAN CAREY